This it not possible atm. You can change it manually in the database table, but that table will be recreated whenever you change something in LinuxMCE that executes the db creation scripts in background.

Why do you need this ? Shouldn't all phone understand inband ? (i'm no expert, just asking)

If you really need this and want it to be included, feel free to open a feature request in trac and i will take care of it as soon as time permits.